The present teachings generally relate to a friction material that can be used in clutch applications, such as a multi-plate wet clutch pack in a limited slip differential system. Friction plates and the friction material on the plates affect the reliability and quality of clutch engagement.
When wet clutches engage and slide against each other, the contacting friction surfaces generate heat. Oil can be applied to the friction plates to cool the contacting components, either by center-fed forced cooling (where oil is pumped through channels in the center of an input shaft and exits through holes in the center of a clutch hub to flow into the clutch pack) or splash cooling (where a differential housing is filled with oil that splashes on the clutch plates). Forced cooling systems allow adjustment of the oil flow rate based on the cooling demand, but incorporating the pump and fluid channels adds complexity to the differential system.
By contrast, splash cooling is a passive cooling method and does not require any special modifications to the differential system. However, the clutch packs in LSD systems are always engaged (e.g., adjacent friction plates and separator plates are always in contact with each other). This makes it difficult for sufficient oil to reach the clutch interface and cool the clutch. In other words, splash-cooled wet clutches tend to have low cooling efficiency.